Superconductivity and localization near a two-dimensional ferromagnetic quantum critical point

We study the influence of disorder on the superconducting transition in a two-dimensional Fermi liquid coupled to the soft Ising-ferromagnetic order-parameter fluctuations associated with proximity to a quantum critical point. We determine the superconducting transition temperature, the temperature dependence of the resistivity, and the phase diagram. The analysis is based on the renormalization group for a modified nonlinear sigma model developed by us in [1]. We demonstrate that diffusion and localization effects drastically modify the interplay between fermionic incoherence and strong pairing interactions leading to a possible strong enhancement of superconductivity, eventually followed by the superconductor-insulator transition.

[1] P. A. Nosov, I. S. Burmistrov, and S. Raghu, 'Interaction-Induced Metallicity in a Two-Dimensional Disordered Non-Fermi Liquid', Phys. Rev. Lett. 125, 256604, (2020).